Navratil, T., D.A. Burns, T. Novakova, J. Kana, J. Rohovec, M. Roll, and V. Ettler.
Chemosphere 208:707-711(2018)

Archived soil samples can provide important information on the history of environmental contamination, and by comparison with recently collected samples, temporal trends can be inferred. Little previous work has addressed whether Hg concentrations in soil samples are stable with long-term storage under standard lab conditions. In this study, researchers re-analyzed a set of archived soil samples that ranged from relatively pristine mountainous sites to a polluted site near a non-ferrous metal smelter with a wide range of Hg concentrations (6-6485 µg/kg). Samples included organic and mineral soils and peats with a carbon content that ranged from 0.2 to 47.7%. Soil samples were stored in polyethylene bags or bottles and held in lab rooms where temperature was not kept to a constant value. Hg concentrations in four subsets of samples were originally measured in 2000, 2005, 2006, and 2007, and re-analyzed in 2017, i.e., after 17, 12, 11, and 10 years of storage. Statistical analyses of either separated or lumped data yielded no significant differences between the original and current Hg concentrations. Based on the analyses, results show that archived soil and peat samples can be used to evaluate historical soil Hg contamination.